Endless playback of a short sequence — looped repeatedly to fill required duration. Standard for background screens and repetitive effects, minimizes rendering.
You know the drill: a short scene needs to repeat endlessly — an elevator ascending, a monitor displaying data streams, waves crashing against the shore. Instead of shooting or generating 30 seconds individually, you take a 3-second sequence and loop it. That's the loop — the oldest editing trick to save time and budget.
In practical workflow: you find or create a scene that is as clean and self-contained as possible. No visible cuts, no pop at the transition — the last frame must seamlessly transition into the first. Then you copy it x times in a row. In editing (Premiere, Final Cut, Avid), this is trivial — stack, duplicate, set ripple length. The computer does the rest. Traditionally, this was actual film technology: you had a physical film loop, a loop of celluloid, that you could place in the projector loop and it would simply run in an endless cycle.
The trick lies in the design of the source material. A loop only works if the cut points are invisible — or if you deliberately stage them (e.g., a continuous camera pan that closes in a circle). This is standard for background monitors, television screens, or stock footage backgrounds. You shoot a sequence that lasts 4, 5, or 8 seconds, and you just play it through — often even layered multiple times with a slight delay in start so it doesn't look robotic.
In the VFX context, loops are used for particle systems, water, smoke, animated textures — material that has no discernible narrative sequence. A 2-second fire animation can be repeated for hours without being noticed. For longer loops or more complex content (like moving people), it becomes critical — then you see the pop, the moment where the repetition begins. Solution: combine several different loops, or mask the loop point with a crossfade. Some editors work with offset loops — several staggered copies of the same sequence, slightly time-shifted, layered, so the repetition becomes invisible.
Today, with infinite computing power and AI-generated assets, the pure loop is less necessary than it used to be — but for budget projects, for stock material, and for quick prototypes on set (e.g., playback on monitors), it's still the tool of choice. Simple, reliable, works on any hardware.